The concept of lights that follow a person can be found at numerous places in literature, film and commercials. A currently used solution, to determine which lights should be activated after each other is to look if two lights are close to each other in physical space but this is not powerful enough; for example in a situation in which two pathways are positioned in parallel, but only separated by a few bushes, the lights will activate as soon as a light near them sees a pedestrian; then the lights on the parallel pathway will activate as well, which is not the intention. The same can be thought of when lights are on two different floors or separated by a thin wall.